Lapping machine

ABSTRACT

A lapping machine in which the horizontal rotating circular disk providing a lapping surface is maintained in a substantially flat or planar condition without the use of truing plates or rings normally used for such purpose. A combined workpiece holder and pressure plate is attached to the lower end of each of a plurality of rotatably driven spindles which are horizontally adjustably positioned along radial lines extending between the axis or centerline of rotation of the lapping surface and the outer periphery of such surface. The plurality of spindles and their respective workpiece holders and pressure plates are positioned along their respective radial lines so that the paths of rotation of workpieces disposed between the lapping surface and the lower surfaces of the combined holders and pressure plates extend about the axis of rotation of the lapping surface in different but somewhat radially overlapping circular paths. Each spindle is rotatably driven by a respectively associated variable speed motor so that the speed of rotation of each respective holder and pressure plate and the workpieces therebelow can be adjusted to compensate for the different rotational speeds of said circular paths extending about the axis of rotation of the lapping surface.

United States Patent McClure [451 Aug. 1, 1972 [54] LAPPING MACHINE [72]Inventor: William J. McClure, Kearneysville,

W. Va.

[73] Assignee: Corning Glass Works, Corning,

[22] Filed: Dec. 10, 1970 [21] Appl. No.: 96,695

[52] U.S.Cl ..51/131 [51] Int. Cl. ..B24b 37/02 [58] Field of Search..51/129, 131

[ 561 References Cited UNITED STATES PATENTS 2,419,739 4/1947 Spina.....5l/l3l 3,518,798 7/1970 Boettcher ..51/131 Primary Examiner-Harold D.Whitehead Attorney-Clarence R. Patty, Jr. and Charles W. Gregg I [57]ABSTRACT A lapping machine in which the horizontal rotating circulardisk providing a lapping surface is maintained of rotatably drivenspindles which are horizontally ad- I justably positioned along radiallines extending between the axis or centerline of rotation of thelapping surface and the outer periphery of such surface. The pluralityof spindles and their respective workpiece holders and pressure platesare positioned along their respective radial lines so that the paths ofrotation of workpieces disposed between the lapping surface and thelower surfaces of the combined holders and pressure plates extend aboutthe axis of rotation of the lapping surface in different but somewhatradially overlapping circular paths. Each spindle is rotatably driven bya respectively associated variable speed motor so that the speed ofrotation of each respective holder and pressure plate and the workpiecestherebelow can be adjusted to compensate for the different rotationalspeeds of said circular paths extending about the axis of rotation ofthe lapping surface.

8 Claims, 7 Drawing Figures PATENTEDAus' 1 Ian Fig. 3* 1 3.680.265 vSHEEI 2 or 5 INVE' 0R. William J. McClure AGENT PATENTEDAus nan3.680.265

Q SHEET 3 U? 5 v INVENTOR. William J. McClure AG'ENT CL L H S 2 7 MNmamm- 1 2 v O 7 6 i w Aw I I INVENTOR. William J, Mc C/qre BY .4 @ZMZM,I AGENT I PATENTEDAUB 1 1972 SHEET 5 [IF 5 INVENTOR. William J. Mp ClareAGENT LAPPING MACHINE BACKGROUND OF THE INVENTION Lapping machines ofheretofore known types require the use of truing rings or plates tomaintain, in a planar condition, the lapping surface provided by ahorizontal rotating circular disk in each such machine. As is well knownsuch lapping surfaces are unevenly worn during lapping operations sothat the lapping surfaces must be frequently dressed to return suchsurfaces to their flat or planar condition for optimum lapping ofworkpieces.

There is, for example, disclosed in US. Pat. No. 2,992,519, issued July18, 1961 to C. 1. Pearson, a polishing apparatus or lapping machine inconjunction with which there is employed a relative massive and heavytruing plate 39 which is used to maintain the surface, layer or face 16of polishing disk 11 exactly true or flat. It will be noted that truingplate 39 has a diameter somewhat larger than the width of the annularupper lapping surface 16 of disk 11 and, therefore, plate 39 overhangsthe inner and outer edges of such annular surface.

As another example, there is disclosed in US. Pat. No. 3,110,988, issuedNov. 19, 1963 to S. A. Boettcher, a lapping machine in whichtruing-retainer rings 46 are employed for maintaining the annularlapping surface 24 of lap wheel or plate 22 in a flat condition at thesame time that lapping or polishing operations are being performed onworkpieces such as W. The diameters of the truing-retainer rings such as46 are also greater than the width of annular surface 24 of lap wheel 22and, therefore, such rings also overhang the inner and outer edges ofsaid annular surface. US. Pat. No. 3,304,662, issued Feb. 21, 1967 to S.A. Boettcher also shows, in FIGS. 1 and 2, the use of truing-retainingrings 30 which are similar to the rings 46 of the prior cited patent toBoettcher.

The truing plates or rings shown in the above cited patents must, ofcourse, be replaced periodically because they are worn down along withthe upper lapping surfaces of the lap disks. In addition, a truing plateas shown in the cited patent to Pearson is relatively difficult tohandle and such plate occupies a station which could be used for anadditional workpiece lapping station. These several factors add to thecost of lapping or polishing operations and, therefore, ways arecontinuously being sought to entirely eliminate the use of truing platesor rings, and/or to substantially reduce the frequency in which thelapping surfaces of lap disks must be dressed to return such surfaces toflat or planar surfaces. Accordingly, the lapping machine of the presentinvention was developed to attain such objects or ends.

SUMMARY OF THE INVENTION In accomplishing the foregoing objects, thereis provided a lapping machine employing an annular rotating lap orlapping disk similar to that employed in previous lapping machines butin which the workpiece holders, or combined workpiece holder andpressure plates or members, are attached to the lower ends ofrespectively associated and individually rotatably driven spindles whichare horizontally movable along radial lines extending between the axisor center of rotation of the lapping disk or lap and the outer peripheryof such lap or disk. Each spindle has associated therewith a spindleassembly or head which supports the respective spindle I and includes avariable speed motor for rotatably driving the associated spindle atselected speeds. The spindles are horizontally movable or adjustable sothey can be staggered across the width of the annular surface of the lapor lapping disk so that workpieces disposed between the bottoms of saidcombined workpiece holders and pressure plates are moved by rotation ofsaid spindles through rotational paths which extend about the axis ofrotation of the annular surface of said lap in different but radiallyoverlapping circular paths. The speed of rotation of each spindle isselected in accordance with its path about said axis so that the speedof movement of each of the workpieces over the annular lap surface issubstantially the same as that of all the other workpieces.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 comprises a top plan view of a lapping machine in accordance withthe invention;

FIG. 2 is a front elevational view of the apparatus or machine of FIG.1, such view being taken generally along line 22 of FIG. 1;

FIG. 3 is an enlarged elevational view of part of the apparatus of FIG.1, such view being taken generally along line 3-3 of FIG. 1;

FIG. 4 isa top plan view of the apparatus of FIG. 3, such view beingtaken generally along line 4-4 of FIG. 3 with an upper part of thestructure shown in FIG. 3 broken away to show details of structure belowsuch upper part;

FIG. 5 comprises a top plan view of one form of a combined workpieceholder and pressure plate adapted for use with the apparatus of thepresent invention, such view being taken generally along line 5-5 ofFIG. 3 and also illustrating a workpiece disposed against the lowersurface of the workpiece holder and pressure plate;

FIG. 6 is an enlarged and detailed elevational view of a part of theapparatus of FIG. 4, such view being partially in cross-section andtaken generally along line 66 of FIG. 4; and

FIG. 7 is an enlarged and detailed top view of the apparatus of FIG. 6,such view being partially in crosssection and taken generally along line7-7 of F IG. 6.

Similar reference characters refer to similar parts in each of thefigures of the drawings.

PREFERRED EMBODIMENT OF THE INVENTION Referring to FIGS. 1 and 2 of thedrawings in detail, there is generally shown a lapping machine 10including an annular lapping or lap disk 11 ofa usual type and having anupper, annular, horizontal and planar lapping surface Ila. Disk 11 issupported on the top of a table 12 which is, in turn, supported by apedestal 13, such pedestal and, thereby, said table and said disk, beingrotatable about a central axis by a variable speed motor means in any ofthe manners which are now old and well known in the art, such motormeans being omitted from the drawings for purposes of simplificationthereof.

A bridge member 16 including a plurality of laterally extending arms 17,18, 19 and 20 spans said planar lapping surface lla generally horizontalthereabove and is supported above such surface by a plurality of uprightlegs or support members such as 21 and 22. Inverted L-shaped spindleassembly support plates 17a, 18a, 19a and a (see FIG. 6) are secured tothe bottoms of arms 17, 18, 19 and 20, respectively, in any convenientmanner, such as by welding for example, and a spindle assembly issecured to the vertical face of each said support plate, the respectiveassemblies secured to support plates 17a, 18a, 19a and 20a beingdesignated 23 through 26, respectively. Spindle assemblies 23 and 24 areidentical in structure to each other while spindle assemblies 25 and 26are also identical in structure to each other as well as being mirrorimages of assemblies 23 and 24. This will be readily apparent from abrief study of FIGS. 1 through 4 of the drawings and, therefore, it isexpedient for purposes of brevity and necessary for an understanding ofthe invention to describe in detail the structure of only one of saidspindle assemblies.

Referring further to FIGS. 1 and 2, taken in conjunction with FIGS. 3,4, 6 and 7, spindle assembly 23 includes a stationary and horizontallyextending track member 30 whose back is secured in any convenientmanner, such as by welding, to the face of support plate 17a which isattached, as previously mentioned, to arm 17 of bridge member 16. Thefront of track member 30 is provided with horizontally extending andsomewhat dovetail shaped projections or tenons which extend intosimilarly somewhat dovetail shaped and horizontally extending grooves ormortises provided in the back of the lower part of a verticallyextending support member 31, such grooves and projections beingcomplemental to each other with a snug but slidable, relationshiptherebetween. Horizontal wear strips and 36 of a hardened and polishedmaterial are disposed between members 30 and 31 and are secured tomember 30 (See FIG. 6). The lower part of support member 31 is providedwith a threaded hole 37 (FIG. 6) into which a first end of acooperatively threaded shaft or rod 38 extends. This will best beunderstood from the corresponding arrangement for member 61 as shown inFIGS. 1, 2 and 3 of the drawings, and including threaded hole 67 andcooperatively threaded rod or shaft 68. The second end of shaft 38extends through and is rotatable in a suitable bearing 39 secured in anyconvenient manner to the face of a bearing support block 40 which is, inturn, secured in any convenient manner to a first or outer end ofhorizontal track member 30 (FIG. 1). A manually actuable crank assembly41 is mounted on shaft 38 at the extreme end of said second end thereof,and manual turning of the crank of the crank assembly 41 will impartcorrespond-v ing rotation to shaft 38 and, thereby, move member 31horizontally along horizontal track member 30 in a directioncorresponding to the direction of said rotation of shaft 38 as will bereadily apparent to those skilled in the art.

Spindle assembly 23 further includes a roller support member 32 which issecured, as by welding, to the front of the lower end of vertical member31 as best shown in FIGS. 6 and 7. A first vertical row of three rollerssuch as 42 (FIGS. 6 and 7) are rotatablymounted on roller support member32 adjacent a first or inner side thereof and a second vertical set ofthree rollers such as 43 are rotatably mounted on said roller supportmember adjacent the second or outer side thereof. A roller contacting orgliding member 34 is secured as by bolts such as 44 (FIG. 7) to the backof a vertically movable spindle support member 33 which is attached, inany suitable manner, to the lower end of the piston rod 46 of areciprocative pressurized fluid motor or cylinder 45 FIG. 3) which is,in turn, mounted on the upper portion of the outer face of previouslymentioned vertical member 31 as by upper and lower clamps 47 and 48partially surrounding the outer periphery of cylinder 45 and secured tosaid outer face of member 31 by bolts such as 49. A stop block 50,similar to bearing support block 40, is attached to the second or innerend of horizontal track member 30 and limits the horizontal movement ofvertical support member 31 in an inner direction, that is, in adirection towards bridge member 16 (FIGS. 3 and 4).

Spindle assembly 23 also comprises a spindle shaft 51 per se which isrotatably supported on the outer face of spindle support member 33 by apair of upper and lower pillow blocks 52 and 53, respectively, which aresecured to said outer face by bolts such as 54. A rotary motor 55 whichis preferably a haudraulically driven motor is also secured on saidouter face of support member 33 as by a clamp member 56 fastened to suchouter face by bolts such as 57. A pulley 55a is suitably keyed to theoutput shaft 55b of motor 55 and a suitable drive belt 58 is loopedaround pulley 55a and a pulley 51a which is suitably keyed to spindleshaft 51. Spindle shaft 51 is preferably a hollow or tubular shaft and arotary union such as 51b is shown mounted on the upper end of shaft 51for the purposes of at times, if so desired, supplying negative pressureor vacuum through such union to the lower end of such shaft. The lowerend of spindle shaft 51 is shown in FIGS. 2 and 3 of the drawings asprovided with a universal coupling 516 for purposes hereinafterdiscussed. Flexible fluid conduits 55c and 5511' are attached to fluidmotor 55 and such motor is rotatively driven in clockwise orcounterclockwise directions accordingly as pressurized hydraulic fluidis supplied to conduits 550 or 55d, respectively, while the other one ofsuch conduits is connected to a reservoir or fluid sink for thehydraulic fluid as is well known in the art.'The driven rotation ofmotor 55 correspondingly drives spindle shaft 51 as is readily apparent,and the speed of rotation of motor 55 and spindle shaft 51 is dependenton the rate of flow of the pressurized hydraulic fluid supplied toconduits 55c or 55d. The lower portion of spindle assembly 23 is shownin FIG. 1 as enclosed in an enclosure 59 but such enclosure is omittedfrom FIGS. 3 and 4 of the drawings for purposes of showing the detailsof the lower portion of the spindle assembly.

From the above description of spindle assembly 23 it will be readilyapparent to those skilled in the art that vertically extending supportmember 31 and, thereby, spindle assembly 23 are horizontally movable orpositionally adjustable along the length of horizontally extending rackmember 30 by the manual operation or rotation of crank assembly 41.Furthermore, as will be readily apparent to those skilled in the art,spindle shaft 51 and the associated parts or members, such as verticalsupport member 33, pillow blocks 52 and 53, motor 55 etc., arevertically movable downwardly and upwardly by piston rod 46 of cylinderor reciprocative cylinder 45.

pressurized fluid motor 45 accordingly as pressurized fluid is suppliedto said cylinder through flexible fluid conduits or pipes 45a and 45b(FIGS. 2, 3 and 4) connected to the upper and lower ends, respectively,of

It is pointed out that, as previously mentioned, spindle assembly 25 isa mirror image of assembly 23 and, therefore, parts or members 30through 51 of assembly 23 correspond to parts or members 60 through 81,respectively, of assembly 25 with the omission of reference numerals 64,66 and 74 since no parts or members of assembly 25 corresponding toparts 34, 36 and 44 are shown in the drawings. Similarly, parts ormembers 75a, 75b, 81a, 81b, 81c, 82, 83, 84, 85, 85a, 85b, 85c, 85d, 86,87, 88 and 89 of spindle assembly 25 correspond, respectively, to partsor members 45a, 45g,5la, 51b, 51c, 52, 53, 54, 55, 55a, 55b, 55c, 55d,56, 57, 58 and 59 of assembly 23.

Spindle-assembly 24 shown in FIGS. 1 and 2 of the drawings is, aspreviously mentioned, identical in structure to spindle assembly 23, andincludes parts and members 90, 91, 92, 93, 97, 98, 99, 100, 101, 102,103, 105, 1050, 105b, 106, 107, 108, 109, 111, 111b, lllc, and 119 whichcorrespond respectively to parts and members 30, 31, 32, 33, 37, 38, 39,40, 41, 42, 43, 45, 45a, 45b, 46, 47, 48, 49, 51, 51b, 51c and 59 ofspindle assembly 23. Similarly, and also as previously mentioned,spindle assembly 26 (FIGS. 1 and 2) is identical in structure to spindleassembly 25, and includes parts and members 120, 121, 122, 123, 128,129, 130, 131, 132, 133, 135, 137, 141, 141b, 1410 and 149 whichcorresponds respectively to parts and members 60, 61, 62, 63, 68, 69,70, 71, 72, 73, 75, 77, 81, 81b, 81c and 89 of spindle assembly 25.

The structure of the machine or apparatus of the invention having beendiscussed above in substantial detail, a brief example of the use of theapparatus or machine in a lapping operation will now be set forth.

As an example of the use of the lapping machine comprising theinvention, it will be assumed that each of a plurality of similarvessels or dishes such as 150 (FIGS. 2, 3 and 5) and having a planarconfiguration such as shown in FIG. 5 are to have their external bottomsurfaces ground or lapped to make such surfaces as substantially flat aspossible. Under such conditions a combined workpiece holder and pressureplate such as 151 (FIGS. 3 and 5) having an outer configurationgenerally corresponding to the configuration of the inner bottom surfaceof the vessels such as 150 is rotatably coupled to the bottom of each ofthe spindle shafts 51, 81, 111 and 141 (FIG. 2) through the respectiveuniversal joints 51c, 810, 1110 and 141C. Each of the workpiece holdersand pressure plates such as 151 is then lowered into the interior 152 ofa suitably positioned and respectively associated vessel such as 150disposed on lapping surface 11a of lap or lapping disk 11 as shown inFIGS. 2 and 3. The lowering of the workpiece holders and pressure platesis accomplished by slowing supplying pressurized fluid, such ascompressed air for example, to conduits 45a, 75a, and 10511, and asimilar conduit connected to the upper end of cylinder 135 of spindleassembly 26 but not shown in the drawings for purposes of simplificationthereof. The above mentioned universal joints allow for self-leveling ofthe bottoms of the vessels such as 150 on the lap or lapping surface 11aof lap disk 11, as is believed apparent.

Following the above described positioning of the vessels such as 150 onthe workpiece holders and pressure plates such as 151, the crankassemblies 41 and 71 are manually rotated to move spindle assemblies 23and 25, respectively, horizontally along their respective horizontalarms 17 and 19 to positions shown, for example, in FIG. 1 of thedrawings, that is, to positions such that the sharply curved cornerareas of the bottom of the vessel at the lower end of spindle shaft 51will move or rotate through a path whose outer limits extend slightlybeyond the outer peripheral edge of lapping surface 11a of disk 11during rotation of shaft 51, and similar corner areas of the bottom ofthe vessel at the lower end of spindle shaft 81 will move or rotatethrough a path whose outer limits extend slightly beyond the innerperipheral edge of lapping surface 11a of disk 11 during rotation ofshaft 81, such outer limits of said paths of rotation being indicated inFIG. 1 by broken line circles designated by reference characters 23a and25a, respectively. (See also FIG. 4 of the drawings). The paths ofrotation of the bottoms of the vessels at the lower ends of spindleshafts 51 and 81 also overlap each other a substantial distance as willbe readily apparent to those skilled in the art from a brief glance atFIG. 1 of the drawings.

The crank assemblies 101 and 131 are manually rotated to move spindleassemblies 24 and 26, respectively, horizontally along their respectivehorizontal arms 18 and 20 to positions such that the bottoms of thevessels at the lower end of spindle shafts 111 and 141 will move orrotate through paths of rotation designated in FIG. 1 by broken linecircles designated by reference characters 24a and 26a, respectively,during rotation of said shafts 111 and 141, such paths of rotationsubstantially overlapping each other as well as overlapping the abovediscussed paths of rotation 23a and 25a. In other words, spindleassemblies 23, 24, 25 and 26 are staggeringly horizontally positionedalong the lengths of their respectively associated transverse supportarms l7, 18, 19 and 20, respectively, so that the bottom surfaces of theworkpieces such as the vessels 150 at the bottom of the respectivespindle assemblies will define different but radially overlapping pathsof rotation about the central axis of lapping surface 11 a of disk 11when such disk and said workpieces are rotated as discussed below. It isalso pointed out that the center of the spindle shaft of each saidspindle assembly moves in a radial line extending through said centralaxis of lapping surface 11a when each respective spindle assembly ishorizontally positioned or moved horizontally along its respectivetransverse arm as mentioned above.

Following the horizontally positioning or adjustment of spindleassemblies 23, 24, 25 and 26 as discussed above, pressurized hydraulicfluid is supplied to the previously discussed fluid conduits connectedto the hydraulically driven motors (such as 55 and of the spindleassemblies 23, 24, 25 and 26, while pedestal 13, table 12, lap disk 11and, thereby, lapping surface 11a of such disk are also rotated by thepreviously mentioned motor means therefor. The rate of flow of thehydraulic fluid supplied to each of the rotary motors of spindleassemblies 23, 24, 25 and 26 is variably controlled by valve means wellknown in the art and such rates of flow in the example presently beingdescribed are adjusted or selected so that spindle shaft 81 is rotatedat the highest speed while spindle shaft 51 is rotated at the lowestspeed. The speed of rotation of spindle shaft 111 is less than that ofspindle shaft 81 but greater than that of spindle shaft'51, while thespeed of rotation of spindle shaft 141 is less than that of both spindleshafts 81 and 111 but also greater than that of spindle shaft 51. Inother words, in the group of spindle shafts 51, 141, 111 and8l taken inthat order, the speed of rotation of each succeeding shaft of such groupis higher than that of the preceding shaft or shafts of the group. Suchvariations or differences in speeds of the spindle shafts are intendedto compensate for the different distances that the centers of rotationof ,such shafts are located from the central axis of rotation of lappingsurface 11a and the resultant different speeds at which such lappingsurface passes under the bottom surfaces of the vessels such as 150 atthe bottom of each of the spindle shafts.

The positions of the spindle assemblies having been selected asdiscussed above, and the speed of rotation of lapping surface 11a and ofthe spindle shafts having been selected or adjusted as also mentionedabove, the apparatus is permitted to reach its said selected speeds andthe lapping of the bottoms of the vessels such as 150 then proceeds. Ifit is decided that such vessels should be pressed against surface 11awith greater pressure, the pressure of the pressurized fluid orcompressed air supplied to the upper ends of cylinders 45, 75, 105 and135 can be increased to supply such greater pressure. Following thecompletion of the lapping or grinding of the bottoms of a group of theves- I sels such as 150 the supply of the pressurized fluids to theapparatus is interrupted'and the rotating parts permitted to come to astop. When this occurs, pressurized fluid or compressed air is suppliedindividually or at the same time to the lower ends of cylinders 45, 75,105 and 135 and the workpiece holders such as 151 are thereby actuatedupwardly out of the interior of the vessels such as 150 which are thenremoved from lap surface 11a and, if desired, replaced by another groupof four vessels such as 150 whose bottom surfaces are to be lapped,polished or ground.

It is pointed out that various types of workpieces can be lapped, groundor polished by changing the workpiece holders attached to the lower endsof the spindle shafts and, in order to accomplish the main object of theapparatus of the present invention, it is necessary to stagger thepositions of the spindle assemblies horizontally along the lengths oftheirrespectively associated transverse supporting arms so thatworkpieces disposed between the lapping surface and said combinedworkpiece holders and pressure plates define or are so disposed indifferent but radially overlapping paths of rotation about the centralaxis of rotation of the lapping surface, and it is then furthernecessary to select or adjust different or varying speeds of rotationfor each of the spindle shafts of the spindle assemblies so that thespeeds of movement of all of the workpieces over the lapping surface aresubstantially equal regardless of the different distances of the spindleshafts from said central axis of the lapping surface. By such anarrangement the lapping surface such as 11a of the apparatus or lappingmachine comprising the invention is maintained substantially flatwithout the use of truing rings, and the necessity for the use of othermeans for periodically dressing or truing said lapping surface bytemporarily removing it from service is substantially reduced oreliminated.

Although there is herein shown and described in detail only one form ofan apparatus or machine embodying the invention, it will be understoodthat various changes and modifications may be made therein with thespirit and purview of the appended claims without departing from thespirit and scope of the invention.

1 claim:

1. in a lapping machine including a lapping disk having an annularhorizontal planar lapping surface rotatable about a central axis, anapparatus for lapping a plurality of workpieces on said lapping surfacewhile simultaneously maintaining such planar lapping surface in a flatcondition, such apparatus comprising;

A. a bridge member spanning said planar lapping surface and including aplurality of laterally extending arms also extending transversely andgenerally horizontally above such lapping surface;

B. a spindle assembly supported on a respectively associated one of eachof said arms for horizontal movement of each such assembly along thelength of its respectively associated arm and each such assemblyincluding,

I. manually operable means for horizontally varying the position of theassembly along its said associated arm,

II. a vertically movable and rotatable spindle,

III. a first motor for reciprocatively and vertically moving the lowerend of the associated spindle toward and away from said lapping surface,and

IV. a variable speed second motor for rotatably driving the associatedspindle; and

C. a combined workpiece holder and pressure plate attached to the lowerend of each said spindle for driven rotation thereby, whereby saidspindle assemblies can, in relation to each other, be staggeringlyhorizontally positioned along the lengths of their respectivelyassociated transverse arms with workpieces disposed between said lappingsurface and said combined workpiece holders and pressure plates tothereby define different but radially overlapping paths of rotation ofsaid workpieces about said central axis of said lapping surface, and therotational speed of the workpieces by each said workpiece holder andpressure plate can be varied to render the speeds of movement of allsaid workpieces over said lapping surface substantially equal to therebymaintain such lapping surface flat while simultaneously lapping saidworkpieces.

2. Apparatus in accordance with claim 1 and in which each said firstmotor comprises a gaseous fluid actuated cylinder and associated pistonrod.

3. Apparatus in accordance withv claim 1 and in which each said variablespeed second motor comprises a hydraulic driven motor.

4. Apparatus in accordance with claim 3 and in which each said firstmotor comprises a gaseous fluid actuated cylinder and associated pistonrod.

5. Apparatus in accordance with claim 1 and in which the path of saidhorizontal movement of each said spindle assembly along the length ofits said which the path of said horizontal movement of each said spindleassembly along the length of its said respectively associated armparallels said lapping surface in a radial line extending from saidcentral axis of such lapping surface to the outer periphery thereof.

8. Apparatus in accordance with claim 4 and in which the path of saidhorizontal movement of each said spindle assembly along the length ofitssaid respectively associated arm parallels said lapping surface in aradial line extending from said central axis of such lapping surface tothe outer periphery thereof.

1. In a lapping machine including a lapping disk having an annularhorizontal planar lapping surface rotatable about a central axis, anapparatus for lapping a plurality of workpieces on said lapping surfacewhile simultaneously maintaining such planar lapping surface in a flatcondition, such apparatus comprising; A. a bridge member spanning saidplanar lapping surface and including a plurality of laterally extendingarms also extending transversely and generally horizontally above suchlapping surface; B. a spindle assembly supported on a respectivelyassociated one of each of said arms for horizontal movement of each suchassembly along the length of its respectively associated arm and eachsuch assembly including, I. manually operable means for horizontallyvarying the position of the assembly along its said associated arm, II.a vertically movable and rotatable spindle, III. a first motor forreciprocatively and vertically moving the lower end of the associatedspindle toward and away from said lapping surface, and IV. a variablespeed second motor for rotatably driving the associated spindle; and C.a combined workpiece holder and pressure plate attached to the lower endof each said spindle for driven rotation thereby, whereby said spindleassemblies can, in relation to each other, be staggeringly horizontallypositioned along the lengths of their respectively associated transversearms with workpieces disposed between said lapping surface and saidcombined workpiece holders and pressure plates to thereby definedifferent but radiaLly overlapping paths of rotation of said workpiecesabout said central axis of said lapping surface, and the rotationalspeed of the workpieces by each said workpiece holder and pressure platecan be varied to render the speeds of movement of all said workpiecesover said lapping surface substantially equal to thereby maintain suchlapping surface flat while simultaneously lapping said workpieces. 2.Apparatus in accordance with claim 1 and in which each said first motorcomprises a gaseous fluid actuated cylinder and associated piston rod.3. Apparatus in accordance with claim 1 and in which each said variablespeed second motor comprises a hydraulic driven motor.
 4. Apparatus inaccordance with claim 3 and in which each said first motor comprises agaseous fluid actuated cylinder and associated piston rod.
 5. Apparatusin accordance with claim 1 and in which the path of said horizontalmovement of each said spindle assembly along the length of its saidrespectively associated arm parallels said lapping surface in a radialline extending from said central axis of such lapping surface to theouter periphery thereof.
 6. Apparatus in accordance with claim 2 and inwhich the path of said horizontal movement of each said spindle assemblyalong the length of its said respectively associated arm parallels saidlapping surface in a radial line extending from said central axis ofsuch lapping surface to the outer periphery thereof.
 7. Apparatus inaccordance with claim 3 and in which the path of said horizontalmovement of each said spindle assembly along the length of its saidrespectively associated arm parallels said lapping surface in a radialline extending from said central axis of such lapping surface to theouter periphery thereof.
 8. Apparatus in accordance with claim 4 and inwhich the path of said horizontal movement of each said spindle assemblyalong the length of its said respectively associated arm parallels saidlapping surface in a radial line extending from said central axis ofsuch lapping surface to the outer periphery thereof.